Apparatus for making paper



Sept. 29, 1970 L, JORDANSSQN ET AL 3,531,371

. APPARATUS FOR MAKING PAPER Filed May 19. 1 966 3 Sheets-Sheet 1 HEATED DRYING-HOOD F/G I INVENTORS.

LARS BE'NGT JORDANSSON, KARL o| o F LARSSOJN a PER BORJE- WAHLSTRQM OR/VEYS Sept. 29, 1970 L. B. JORDANSSON ET -3 ,31,3 71

- APPARATUS FOR MAKING PAPER Filed May 19. 1966 3 Sheets-Sheet 2 FIG. 3

INVENTORS. LARS BENGT 'JORDANSSON, KARL OLOF LARSSON a PER BORJE WAHLSTROM ihelr Y ATTORNEYS Sept. 29, 1970 L. B. JORDANSSON ETA!- 3,531,371

APPARATUS FOR MAKING PAPER 7 Filed May 19. 1966 3 Sheets-Sheet 5 INVENIORS. LARS BENY'GT JORDANSSON, KARL-PLOF LARssoN a PER BOR-JEWAHLSTROM B) @da-M I [I'M iheir- ATTORNEYS United States Patent Office US. Cl. 162298 16 Claims ABSTRACT OF THE DISCLOSURE A paper-making machine according to the exemplary embodiments comprises a moving impermeable surface, which may be either a cylinder or a movable endless belt, upon which a fibrous stock is deposited and formed into a Web. The web is pressed to partially dry it, and is then exposed to heat to further dry it, preferably substantially completely. All of these steps, forming, pressing and drying, are accomplished on the impermeable surface so that the finished web is removed for a final drying, if necessary, or for winding into a roll. The apparatus includes a movable, endless, foraminous belt defining with the impermeable surface a web-forming space and is arranged adjacent the impermeable surface to squeeze water from the stock. The drying equipment includes a heated chamber positioned adjacent the surface for heating the web to evaporate the moisture from it.

This invention relates to novel and improved apparatus for making paper.

In one conventional method of making paper a fiber stock is formed into a web in a special machine unit, for instance a Fourdrinier wire section, and is transferred from the wire section for further water removal and drying to other machine units, such as a press section and a dryer section. Another type of web-forming unit known in the art comprises a solid forming roll and a wire stretched along part of the periphery of the solid roll (US. Pat. 3,056,719), or between a Wire and a felt, both of which are stretched along the periphery of a solid or perforated forming roll. Machines of this type may also include systems for dewatering the web by suction or pressing against the forming roll before the web is transferred to a press or drying section. In most paper making machines, the web is transferred from one machine unit to another, either in an open draw or supported by a felt between said machine units, several such transfers often being made in the course of the paper production process.

Both open-draw and felt transfer have significant disadvantages. For example, an open draw subjects the web to relatively large tensile stresses, those stresses being greater at higher running speeds; there is always a danger of a break at the open draw, and an open draw often constitutes a limit on machine speed in order that tensile stresses in the web will be kept at acceptable levels. In transferring the web with a felt, the web is generally picked olf the wire by a vacuum roll within the felt and is conveyed to the press or dryer adhered by surface tension forces to the undersurface of the felt. A transfer on a felt is generally a delicate operation involving fairly critical conditions such as the condition of the felt, the felt structure, and the moisture content of the web and felt. Maintenance of sufficient surface tension to hold the web on the felt requires a relatively highly moistened felt which, of course, adversely affects the moisture content of the web.

In some paper machines the formed paper web is transferred from the web-forming wire section to a heated Patented Sept. 29, 1970 drying cylinder, generally called a yankee cylinder, by means of a felt. The paper web carried on the felt is pressed against the surface of the drying cylinder and the felt taken off, thus leaving the web adhered to the drying cylinder. The paper web is then dried in one stage on the drying cylinder by heating it until it is sufliciently dry that it can be removed in an open draw or by means of a doctor blade. In order that the drying be as eflicient as possible, it is of importance that the resistance against heat transfer between the surface of the drying cylinder and the paper be as small as possible. This is accomplished by good contact between the surface of the cylin der and the paper web. Also, it is advantageous that the moisture content of the paper web be as low as possible when it is pressed against the cylinder surface so that the amount of Water which has to be evaporated is moderate.

In this regard a high temperature in the paper web is advantageous because the viscosity of the water will then be relatively low. When there is contact between the paper web and the surface of the drying cylinder, heat passes from the cylinder surface to the paper so that the water in the portion of the paper web which is closest to the cylinder surface evaporates and diffuses through the paper towards its outer free surface, i.e. the surface which is remote from the surface contacting the cylinder. However, at high drying cylinder temperatures the instantaneous evaporation may be so high that the steam pressure reduces the contact between the cylinder surface and the paper, thus the resistance to heat transfer increases. In order to prevent such momentary high evaporation one can cool the cylinder surface by blowing onto the surface a medium which removes heat from the part of the cylinder immediately ahead of the point where the paper web is brought into contact with the cylinder.

This invention relates to a novel and improved papermaking machine which does not have the disadvantages of previously known machines, such as the difliculties encountered in transferring a paper web between the several machine units for forming, pressing, and drying the web, and in establishing and maintaining good contact between the paper web and a drying surface. In the apparatus of the invention a continuous fiber web is formed in a sheet-forming zone defined by the surface of a moving foraminous member and an endless moving, impermeable forming surface, which may be either the surface of a cylinder or an endless belt. In other Words, the apparatus of the invention comprises means defining an endless impermeable surface, means mounting the surface for movement along a predetermined path, and means for continuously moving the surface along such path in one direction. After the web is formed, it remains adhered to the forming surface and is partly or fully dried on the forming surface by means of heat without being separated from it.

One advantage of the machine of the present invention is that it is of simple construction, consisting of one single machine unit in which the paper web is formed, pressed, and dried, all while it is in contact with the same continuous forming surface. Because of its simple construction, the capital investment is reduced; because it is simpler to operate, labor costs are lower. Further savings in labor and materials are afforded by less frequent replacement of felts and wires than in conventional machines, and shutdown time on the machine, being significantly less than normal, affords a greater output per machine. The operating speed is generally limited only by the drying time, as compared to the strict limitations usually necessitated in conventional machines by web transfer considerations. With some types of paper and with a machine having, for example, a drying cylinder with a diameter of 15 to 20 feet, speeds of 5000 ft./min. or

3 more are attainable. Thus, the machine of the invention provides a higher output at lower unit cost.

For a better understanding of the invention, reference may be made to the following description of exemplary embodiments, taken in conjunction with the figures of the accompanying drawings, in which:

FIG. 1 is a side view, in generally schematic form, showing an embodiment of the invention in which the forming surface is constituted by the surface of a drying cylinder;

FIG. 2 is a schematic side view of an embodiment similar to FIG. 1, except that the forming surface is an endless belt;

FIG. 3 is a schematic side view of an embodiment similar to FIG. 2, except that a different web-forming unit is provided;

FIG. 4 is a schematic side view of another embodiment of the invention, the embodiment being similar to that of FIG. 1 except that it includes a multiplicity of units for forming the fiber web on the drying cylinder; and

FIG. 5 is a schematic side view of an embodiment of the invention similar to that of FIG. 2, except that it incorporates two units for forming the web on the belt surface.

In the drawings, the same reference numerals are used in each figure to designate the equivalent parts of the several embodiments, letter suffixes being used, however, to differentiate between the several embodiments. The letter suffixes a through e are used in the drawings to designate the elements of each of the embodiments of FIGS. 1

to 5, respectively.

In the embodiment of the invention shown in FIG. 1, the paper web is formed, pressed and dried on the surface of a drying cylinder 120, which may, preferably, be a so-called yankee cylinder of generally conventional construction; the drying cylinder 12a is internally heated, by means for heating the cylinder, and because it is a circular cylinder, it has a convexly curved surface. Such convexly curved, impermeable surface is mounted, as by its shaft and body or end members, for movement along a predetermined path. The rotation of the cylinder (as described below) causes such impermeable surface to move along such predetermined path in one direction. The web is formed in a forming space defined between the surface of the cylinder 12:: and a portion of a foraminous member, such as a wire 14a stretched along first part of the path of movement of the cylinder surface and carried by idler rolls 16a to 19a and a tension roll 20a, such first portion being convexly curved by virtue of the convexly curved form of such cylinder surface. The cylinder is rotated and the wire moved, in the directions indicated by the arrows, at equal 1 speeds (i.e., the wire and forming surface are moved conjointly) and a suspension of the fibers which will make up the formed web 10 is delivered into the forming space between the wire and cylinder from a head box 22a in the form of a thin stream or jet. The jet enters the upstream end of the forming space, which is tapered in the direction of movement of the Cylinder surface and the wire, and is then subjected to pressure established by the tension in the wire 14a such that a portion of the water is squeezed out through the wire and a web of uniform thickness formed. The water pressed out of the suspension in the webforming zone is collected in a water box 240. The characteristics of the web are determined by such factors as the thickness, consistency and delivery rate of the fiber suspension, the speed of the cylinder and wire, and the pressure of the wire against the fiber suspension.

Upon leaving the forming space, the web remains adhered to the surface of the cylinder 12a and passes through one or more press means for pressing the web against the cylinder surface, such as a press unit 26a. Such press means is positioned at a location adjacent the cylinder surface at a location adjacent the cylinder surface downstream from the downstream end of the forming space. The press unit comprises a press ro-ll 28a and a felt 30a, the felt being guided around the press roll 28a, idler 4 rolls 32a and 33a, and a tension roll 34a. The press may include apparatus for cleaning and dewatering the felt. As the web passes through the nip between the cylinder 12a and the press unit 26a, an additional amount of water is removed.

The web 10, which still remains adhered to the surface of the cylinder, passes from the press unit and moves through a drying zone at a second portion of the path of movement of the cylinder surface, such second portion being spaced and downstream from the aforesaid first portion, in which it is dried by evaporation by applying heat from heating means that includes a heated drying hood in facing relation to the forming surface. In particular, the drying zone affords water removal by the application of heat from both the heated drying cylinder 12a and a heated drying hood 36a. Upon leaving the drying hood 36a, the web, which may be partially or completely dry, is removed from the surface of the cylinder 12a, either by pulling it off or by means of a doctor blade 38a, as shown, located downstream from the second portion of the impermeable surface (where the drying hood is located) and upstream from the first portion of the impermeable surface (where the forming zone is located), relative to the direction of movement of the impermeable surface. In the illustrative embodiment of FIG. 1, the web 10 is then guided away in a fully dried condition and wound onto a take-up roll 4011, but it is within the scope of the invention to take the web in a partially dry state from the cylinder for additional drying on another cylinder or for other operations.

It should be noted that in the machine of FIG. 1, because the paper web is formed between a wire and a part of a continuous forming surface on Which the Web is dried, a certain amount of heating of the web takes place in the forming and pressing zones. The water in the web which is nearest to the warm surface of the cylinder tends upon heating to displace the water which is more remote from the surface of the cylinder outwardly. The result is a fairly uniform temperature increase across the entire thickness of the web. The preheating of the web also results in a lowering of the temperature of the forming surface, thereby leading to a more moderate rate of steam formation during the early stages of drying. Accordingly, good contact between the paper Web and the cylinder surface is obtained and is maintained throughout the drying process. The homogeneous preheating of the web also has the result of reducing the viscosity of the water in the stock and thereby improves the Water removal process in the press unit 26a.

In the embodiment of FIG. 2, the impervious surface on which the web is both formed and dried is constituted by a moving continuous steel belt 12b which is carried by a pair of spaced-apart cylinders or carrier rolls 13b and 13b, one of which is driven to move the belt in the direction indicated by the arrow. In other words, the belt, and thus its impervious surface, is mounted for movement along a predetermined path by cylinders 13b and 13b, and means (a drive roll) is provided for moving the surface along such predetermined path in one direction. The fiber stock is introduced from a head box 22b into a forming space defined between a moving wire 14b and a first portion of the surface of the belt 12b, such first portion being in the region where it is guided around the cylinder 13b. By virtue of the curvature of the carrier roll, such first portion is a convexly curved portion. The formed web, which remains adhered to the belt 12b upon leaving the forming zone, is further dewatered by a press unit 26b and is then partially or fully dried on the belt 12b in a drying chamber 36b that is located along a run of the belt between the carrier rolls and spaced from the carrier rolls and includes sections located in opposed relation on opposite sides of the belt, all as shown in FIG. 2.

The embodiment of FIG. 3 is very much like the embodiment of FIG. 2 and comprises a moving steel belt carried by a pair of spaced apart carrier rolls 13c and 13c. A fiber suspension is conducted from a head box 22c into the space defined between the upstream end of a belt 120 and a moving wire 140. In the forming zone, the belt 120 traverses the lower surface of a fixed back-up support 15c. Moreover, the width of the forming space is defined, not by the pressure of the wire 14c, but by the physical position of a wire back-up member or guide 150' positioned behind the wire 14c. The forming space is tapered in the direction of movement of the belt, as shown in FIG. 3. The upper surface of the back-up 15c may be a grid work, a perforated plate or the like, and the lower portion of the back-up 15c may be a chamber for collecting water squeezed out of the fiber suspension and through the wire and back-up 15c. The web is transported from the forming zone adhered to the lower surface of the belt 120 and passes through a press unit 260, the press roll 280 being backed up by a back-up roll 29c positioned above the belt. The partially dried web is then carried from the press through a dryer 36c and removed by a doctor blade 380.

The embodiment of FIG. 4 is similar to FIG. 1 except that it provides for multi-stage sheet forming. A heated drying cylinder 12d includes a web-forming zone constituted by two separate web-forming spaces, each of which is defined between a portion of the surface of the drying cylinder 12d and a moving wire 14d, or 14d. A fiber suspension is fed from a first head box 22d into the space between the first wire 14d and cylinder 12d and a second fiber suspension, which may be the same as or different from the first, is delivered from a second head box 22d into the space between the second wire 14d and the cylinder 12d. The second stream from the jet 22d merges with the previously formed web coming from the first forming space and forms a unitary web d by reason of the delivery and formation of a second stock layer in overlying relation on the web formed between the cylinder surface and the first wire 14d. The web, upon leaving the second forming wire unit 14a" adheres to the cylinder and passes through a press unit 2611 and a drying hood 36d. In the embodiment of FIG. 4, the first foraminous belt 14d is located adjacent a first portion of the cylinder surface, the drying hood 36d is located adjacent a second portion of the cylinder surface, and the second foraminous belt 14d is located adjacent a third portion of the cylinder surface intermediate the first and second portions. Both foraminous belts are tensioned toward the cylinder surface to define web-forming spaces that are tapered in the direction of movement of the cylinder surface and the foraminous belts.

In the embodiment of FIG. 5, an impervious moving steel belt He is led around first and second cylinders or main carrier rolls 13e and 1312', each of which has associated with it an endless foraminous belt or a forming wire unit 142 and 142', respectively, and around a series of carrier rolls 42e, 43c, and 44s; the roll 42c has a surface, such as provided by a wire sleeve, which resists adherence of the web to prevent the web from being picked up by it. The web 10e is formed in two stages by introducing a fiber suspension from respective head boxes 22c and Me in a manner similar to the embodiment of FIG. 4. Upon leaving the second forming wire 142, the web is pressed against the surface of the cylinder 13e' by a felt press unit 26c and is dried by passing it through a drying chamber 362. In both the embodiments of FIGS. 4 and 5, additional forming wires can be provided, and the embodiment of FIG. 5 could employ forming units of the type shown in FIG. 3.

As shown in FIG. 5, the first foraminous belt 14a is located adjacent a first portion of the impermeable belt, such first portion being at a location along the run of the belt where it turns around one of the carrier rolls 13e. The drying hood 36c is located along a second portion of the run of the impermeable belt, and the second foraminous belt is located at a thirdportion of the run of the impermeable surface intermediate the first and second portions. Such third portion is located along a part of the run of the 'belt where it turns around the carrier roll 13a. The carrier roll 42c is located to form a concave loop in the belt intermediate the main carrier rolls 13c and 13a, and the head box 22:: that supplied stock to the forming space between carrier roll 13c and the wire 14e is located within such loop of the belt within that third carrier roll 422.

A considerable number of tests have been run on a pilot machine similar to that shown in FIG. 1. In the pilot machine, the drying cylinder 12a has a diameter of nine feet and a width of three feet. The drying hood is direct fired and can be heated to temperatures of up to about 600 F. The machine can be run at variable speeds up to 4,000 feet per minute surface velocity. In making a 14 lb. per 3,000 square feet basis weight web, it has been found that the paper can be fully dried at speeds up to 1,000 feet per minute. For other paper stocks between 10 and 30 lbs. per 3,000 square feet basis weight, running speeds have varied between 1,000 and 3,000 feet per minute. Stock consistencies of between 0.1% and 1% have been run. At higher machine speeds, the paper has been removed from the machine less than fully dried and fully dried on another drying cylinder. This permits higher operating speeds.

Experiments have shown that the dryness of the web upon leaving the forming wire section varies from about 5% to 15%, depending upon the basis weight. The dryness of the web after leaving the press unit varies widely, depending upon both the basis weight and running speed, but drynesses of as much as 40% have been obtained. In general, the experiments conducted on the pilot machine have shown very satisfactorily the versatility and efiiciency of the machine of the invention. It has been shown that papers of up to and perhaps in excess of 30 lbs. per 3,000 square feet basis weight can be made on the machine, and that it is particularly well suited for lighter grades of papers such as those classified as tissues, toweling and MG papers.

The above described embodiments of the invention are merely exemplary, and those skilled in the art will be able to make many modifications and variations of them with out departing from the spirit and scope of the invention. All such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

We claim:

1. Apparatus for making a fibrous web comprising means defining an endless impermeable surface, means mounting the surface for movement along a predetermined path, means for continuously moving the surface along such path in one direction, a movable endless foraminous belt mounted for movement along a path bringing a portion of the foraminous. belt into adjacent spaced relation to a first portion of the path of movement of the impermeable surface and to define with such first portion of the path of movement of the impermeable surface a web-forming space that is tapered in the direction of movement of the surface, the said foraminous belt being moved conjointly with the impermeable surface at the said first portion of the path of movement of the impermeable surface, means for introducing a fibrous stock into the web-forming space at the upstream end thereof, relative to the direction of movement of the impermeable belt, whereby a web is formed on the impermeable surface, and heating means adjacent the impermeable surface at a second portion of the said path of movement thereof and in facing relation to the web for at least partially drying the web while it remains on the impermeable surface.

2. Apparatus according to claim '1 wherein the means defining the impermeable surface is a circular cylinder,

7 and wherein the heating means includes means for heating the cylinder.

3. Apparatus according to claim 1 wherein the path of movement of the impermeable surface includes at least one convexly curved portion, and wherein the portion of the foraminous belt defining the said web-forming space is located adjacent the said convexly curved portion of the impermeable surface.

4. Apparatus according to claim 1 wherein the means defining an impermeable surface includes an endless impermeable flexible belt and at least two spaced-apart carrier rolls around which the impermeable flexible belt is trained.

5. Apparatus according to claim 4 wherein the portion of the foraminous belt defining the web-forming space is located adjacent a portion of the said path of move ment of the impermeable flexible belt where it is trained around one of the carrier rolls.

6. Apparatus according to claim 1 and further comprising press means located downstream from the said first portion and upstream from the second portion of the impermeable surface, relative to the direction of movement thereof, for pressing the web against the impermeable surface to remove liquid therefrom.

7. Apparatus according to claim 1 and further comprising a second endless foraminous belt mounted for movement along a path providing for a portion thereof to be in adjacent spaced relation to a third portion of the path of movement of the impermeable surface and to define with the surface at such third portion a web-forming space that is tapered in the direction of movement of the impermeable surface, said third portion of the path of movement of the impermeable surface being located downstream of the first portion and upstream of the second portion of the impermeable surface, the second foraminous belt being moved conjointly with the impermeable surface, and means for introducing fibrous stock into the web-forming space defined by said second foraminous belt at the upstream end thereof, relative to the direction of movement of the impermeable surface, whereby a second layer of stock is deposited over the web formed in the web-forming space defined by the first foraminous belt, thereby to form a multi-layer web on the impermeable surface.

8. Apparatus for making a fibrous web comprising a circular cylinder having an impermeable surface and mounted for rotation to move such surface continuously in one direction, a movable endless foraminous belt mounted for movement along a path to bring a portion thereof into adjacent spaced relation to a first portion of the cylinder surface and to define with such first portion a web-forming space that converges in the direction of movement of the cylinder surface, the foraminous belt being tensioned to urge the said portion thereof toward the cylinder surface and thereby express liquid from a fibrous stock introduced into the web-forming space, means for introducing a fibrous stock into the web-forming space at the upstream end thereof, relative to the direction of movement of the cylinder surface, whereby a web is formed on the cylinder surface, press means for pressing the web against the cylinder surface at a location adjacent the cylinder surface downstream from the downstream end of the web-forming space, relative to the direction of movement of the cylinder surface, for removing liquid from the web carried on the cylinder surface, and means disposed adjacent a second portion of the cylinder surface downstream from the press means for heating a web on the cylinder surface to a temperature sufficient to evaporate moisture therefrom and to at least partially dry the web while it remains on the cylinder surface.

9. Apparatus according to claim 8 wherein the heating means further includes means for heating the cylinder.

10. Apparatus according to claim 8 and further comprising a second endless movable foraminous belt dis posed adjacent the cylinder surface and having a portion defining with a third portion of the cylinder surface intermediate the first and second portions a web-forming space that is tapered in the direction of movement of the cylinder surface, and means for introducing fibrous stock into the upstream end of the web-forming space defined by said second foraminous belt, the second foraminous belt being tensioned to urge the said portion thereof against the cylinder surface to express liquid from the stock introduced therein and thereby to form a stock layer in overlying relation on the web formed in the first web-forming space.

11. Apparatus for forming a fibrous web comprising a moveable endless impermeable belt, first and second spaced-apart carrier rolls carrying the belt for continuous movement in one direction, a movable endless foraminous belt having a portion thereof disposed in spaced relation to a first portion of the impermeable belt to define therewith a web-forming space that is tapered in the direction of movement of the impermeable belt, means for moving the impermeable belt and the foraminous belt conjointly, means for introducing a fibrous stock at the upstream end of the web-forming space, relative to the direction of movement of the belt, whereby a fibrous web is formed on the impermeable belt as the stock moves with the belt through the tapered web-forming space, press means located adjacent the impermeable belt at a location downstream from the said first portion for pressing the web against the impermeable belt to remove liquid therefrom, and means including a heated drying hood positioned adjacent a second portion of the impermeable belt downstream from the press means and heated to a temperature sufiicient to heat the web and evaporate moisture therefrom to at least partially dry the web while it remains on the impermeable belt.

12. Apparatus according to claim 11 wherein there is a run of the impermeable belt extending along a substantially straight path between the carrier rolls, and wherein the first and second portions of the impermeable belt are located along the said straight run of the impermeable belt.

13. Apparatus according to claim 11 wherein the first portion of the impermeable belt is along a portion of the perimeter of one of the said carrier rolls, and wherein the foraminous belt is tensioned to urge the said portion thereof defining the web-forming space against the impermeable belt to express liquid from the stock delivered into the Web-forming space.

14. Apparatus according to claim 13 and further com prising a second endless foraminous belt having a portion located adjacent a third portion of the impermeable belt intermediate the first and second portions thereof, the said portion of the second foraminous belt defining with said third portion of the impermeable belt a second webforming space that is tapered at the direction of move ment of the impermeable belt, and means for delivering fibrous stock to the upstream end of the second web-forming space thereby to form in such second web-forming space another layer of a web in overlying relation on the layer formed in the first web-forming space.

15. Apparatus according to claim 14 wherein the first and third portions of the impermeable belt are located in regions of the path of movement of the belt where the belts are trained around the said carrier rolls, and wherein the foraminous belts are tensioned to urge the said portions thereof against the impermeable belt to express liquid from the stock in the said web-forming space.

16. Apparatus according to claim 15 and further com prising a third carrier roll around which the impermeable belt is trained and by which a concave loop of the impermeable belt is formed intermediate the first and second carrier rolls, and wherein the means for delivering 9 10 fibrous stock to the second web-forming space is located S. LEON BASHORE, Primary Examiner wrthrn the concave loop of the lmpermeable belt. R- H. TUSHIN Assistant Examiner References Cited UNITED STATES PATENTS 5 3,397,112 8/1968 Highton et a1. 162-203 XR 7, 300, 314, 317, 318 3,056,718 10/1962 Grisson et a1. 162-206 XR 3,354,035 8/1967 Gottwald et a1 162-206 

